A power circuit breaker having an interrupting rating higher than the type of switchgear apparatus which is commonly referred to as a recloser, is still required to have the ability to immediately re-close at least once after a trip. Thus, when this so-called "open-close-open" feature, or OCO, is required on a circuit breaker which has just been closed, the charging of a closing spring, which was discharged to close the circuit breaker, must be re-charged so that the circuit breaker can be immediately closed following a subsequent trip. This feature of a power circuit breaker provides substantially continuous electrical service for customers of a large block of electrical energy handled by the power circuit breaker, when a momentary power surge, such as a surge caused by lightning, initiates a trip operation.
Circuit breaker operating mechanisms of the prior art which are constructed to store closing energy after the circuit breaker has been closed, generally use a cam and cam follower arrangement. The cam is contoured such that the shaft on which the cam is mounted can be turned to charge a closing spring while the cam follower, which is holding the circuit breaker closed, is held by the cam at a substantially constant radial position. U.S. Pat. No. 4,163,133, which is assigned to the same assignee as the present application, discloses such a prior art cam arrangement.
While the prior art cam arrangement operates satisfactorily, the closing springs may be called upon to be charged over relatively long periods of time, requiring the cam, cam follower, associated shaft and bearings to all be constructed to continuously withstand the high closing spring forces without damage to the operating mechanism, adding significantly to the cost of the mechanism.
Due to the high forces and frictions involved in the cam arrangement, the mechanism associated with the operation of the cam arrangement must also be sophisticated, and therefore costly, in order to prevent freezing-up of the cam arrangement when it is called upon to operate after long periods of withstanding the forces of a charged closing spring.
Cam arrangements also require that the cam and cam follower be precisely located relative to one another, and relative to other parts of the operating mechanism, increasing the manufacturing and assembly cost, as well as complicating maintenance.
Thus, it would be desirable, and it is an object of the invention, to provide a new and improved operating mechanism for a circuit breaker which will provide circuit breaker operating functions similar to those obtainable with the hereinbefore mentioned cam arrangements, including the open-close-open characteristic, while simplifying and reducing the cost of the operating mechanism, all without sacrificing operability and reliability.
Circuit breakers of the types described above, must have the option of being able to electrically charge the closing spring. The charging motor, once it has charged the closing spring to the proper position, must be prevented from continuing to charge the spring. Prior art approaches use brakes, and other costly means to limit rotation of the motor once the desired spring charge has been achieved. It would be desirable, and it is another object of the invention, to provide electrical charging means for the closing spring which eliminates the need for braking the charging motor, thus reducing the cost and complexity of the electrical charging function.